Comments by Nadunwow (Top 1 by date)

Thank you for the quick answer.
The problem is I have not used CONSTRAINT here.

if I have used CONSTRAINT here we can do that method.

Any way use method gives me this error message

Msg 3728, Level 16, State 1, Line 1
'studentID' is not a constraint.
Msg 3727, Level 16, State 0, Line 1
Could not drop constraint. See previous errors.